This article reviews the epidemiologic impact of the immunization policies in Belgium since the time efficacious vaccines became available, including recent serologic and virologic surveys as well as evidence for the relative effectiveness of inactivated poliovirus vaccine (lPV) and oral poliovirus vaccine (OPV) in routine immunization programs. Poliomyelitis as an indigenous disease has disappeared in Belgium since the late 1960s as a result of immunization with IPV from 1958 to 1969 and with OPV since 1963. In the immediate prevaccine era, the annual average number of cases of paralytic poliomyelitis per million inhabitants was 37 between 1951 and 1954 and 71 between 1955 and 1958, with a peak of 1,038 cases in 1956. Soon after the initial successful control of poliomyelitis in the early 1960s, the acceptance rate of vaccination decreased. In order for a high level of immunity to the disease in the population to be maintained, immunization of children before the age of 18 months was made compulsory by Royal Decree on January 1, 1967.